Planographic printing sheet



June 13, 1950 D. A. NEWMAN 2,511,783

PLANOGRAPHIC 'PRINTING SHEET Filed Feb. 28. 1946 ATTORNEYS Patented June 13, 1950 UNITED STATES PATENT OFFICE PLAN OGRAPHIC PRINTING SHEET Application February 28, 1946, Serial No. 651,002

This invention relates to the art of planographic printing, and more particularly to a novel and improved printing plate or sheetthis application being a continuation in part of my application Serial No. 459,629, filed September 25, 1942, now abandoned.

It has been proposed heretofore to provide a planographic printing plate by laminating two parchmentized sheets of desired thickness together in an effort to prevent distortion of the images due to expansion and contraction of the sheets when wet by water in their use. This laminating has been done by pressing the amyloid surfaces of the acid treated sheets together after they have been washed and before they are dried in making the sheets, and by securing the parchmentized sheets together by waterproof adhesives.

In neither case have consistent satisfactory results been obtained, probably because, in the first-mentioned method, moisture eventually passes from the working lamination when exposed to water to the then backing lamination and resistance to distortion which the latter is intended to prevent becomes reduced or ineiective. In the method using waterproof adhesive, the latter provided an ineffective bond between the laminations by not penetrating the adjacent amyloid surfaces of the sheets, or, if designed to penetrate the parchmentized surface, did so to an uncontrollable extent and interfered with the desired hydrophilic properties of the outer ci' working surfaces of the sheets.

These difficulties have been avoided by the present invention by providing two sheets, each of which is parchmentized on one side only and to an approximate predetermined depth, bringing the unparchmentized surfaces of the sheets v sheets impregnated and bonded together by the waterproof adhesive material and into or through which the moisture applied to the working surface of the plate in its use can not penetrate. Being thus unaffected by moisture, the inner adhesive-impregnated fibrous stratum holds'the working surface fiat and to its original desired dimensions.

The adhesive is of such character that it does not alter substantially the' flexibility of the two sheets taken collectively and hence the laminated sheet may be conveniently wrapped around a typewriter platen to receive type impressions.

The adhesive may be applied in such quantity or be of such quality that a thin film of adhesive material between the two plies of the plate results, or it may be such that no perceptible stratum of adhesive exists at the interface of the two plies.

According to the present invention, the planographic plate may have its opposite faces so formed that each has a different kind of surface and hence the one best suited for a particular job may be selected for use. For example, one surface may be an unmodified parchment surface while the other may be treated or coated with material providing a desired grain or tooth thereon.

It should be understood that after one surface of my improved printing plate has been used for planograph reproduction of an image inscribed or imprinted thereon, the -opposite surface can be used for planographic reproduction of additional image-'forming inscriptions, thus reducing the plate cost by one half. For example, one surface of the sheet can be modified as set out above with a coating rendering it especially suitable for an image formed by a wax pencil or lithographie crayon, while the other surface is especially adapted for reception of a typewritten or printed form.

It was known heretofore to attach a paper backing by means of a waterproof adhesive to a planographic sheet, but by reason of the different character and properties of the sheet and backing, they were affected by the aqueous inkrepellant fluid or atmospheric moisture to different degrees, and therefore had a strong tendency to curl in damp or dry condition, which is particularly troublesome when it is desired to ille them at for future use. By reason of the substantially symmetrical structure of the plates of my invention, the foregoing diiiiculty is completely avoided, and the plates have no tendency to curl in wet or dry condition.

In the present invention two sheets of paper are parchmentized on one side only, so that a layer of amyloid is formed on one side extending inward preferably from about one-third to about one-half of the thickness of the paper. A waterproofing adhesive is applied to the opposite unparchmentized sides of the paper sheets and these surfaces are brought together by any of the methods known in the laminating art. However, a sumcient quantity of adhesive is preferably employed so that it will penetrate and substantially saturate the unparchmentized Nlayers of said sheets, thus impregnating the sheets preferably to a depth of about one-half to two-thirds of their thickness, the amyloid layers preventing further penetration of the adhesive to the planographic surfaces.

In Fig.-1 of the accompanying drawings, I show an enlarged section of a fragment of one sheet` of paper, parchmentized on one side, as employed in making the planographic plates of my invention. The sheet comprises a layer I of amyloid, extending inward from the upper surface to a depth equal to about one-third of the thickness,

of the sheet. The underlying unparchmentized layer II retains its original relatively porous flbrous structure.

In Fig. 2 o. he accompanying drawing, I show an enlarged section of a fragment of a planographic plate embodying my invention, wherein two sheets of the type shown in Fig. 1 are laminated together with the unparchmentized layers II in contact, said layers being held together by waterproof adhesive I2 which impregnates and preferably saturates the layers I I, substantially to their full depth, thus extending to the inner limits of the amyloid layers l0. Preferably the adjacent surfaces of the sheets are pressed into close and intimate contact so that there is practically no separate layer of adhesive between the two sheets, and the resulting sheet is in effect similar to a single sheet of double thickness paper, having a layer of amyloid on both sides and a core of unparchmentized fibre impregnated with waterproofing material.

Such a sheet, being of balanced construction, i. e. similar on its two sides with respect to their reaction toward water or moisture, has no tendency to curl when wet or dried, as distinguished from composite sheets heretofore known in which the layers were of dierent character.

The quality and thickness of the semi-parchmentized sheet of Fig. 1 employed in making the planographic plates of this invention can be varied in accordance with the nature of the image, length of run" or number of copies to be made, and construction of the duplicating machinery. The sheets can be calendered to provide a smooth surface. When longer runs are to be made, and if the image is typed or imprinted on the printing surface, I prefer to use semi-parchmentized paper having a highly plated or smooth polished surface yfor reception of the 'planographic image. Relatively heavier sheets are generally more desirable for longer runs, but in view of the water-resistant properties of the core and distortion-resistant properties of the finished plate, a much lighter construction can be used than was possible heretofore for producing a given number of copies.

The waterproofing adhesive can be applied in molten state or in solution in a solvent for impregnating and laminating together the unparchmentized surfaces of the sheets. Suitable adhesive waterproofing materials include, for example, paraihn wax alone or in combination with other waxes, or with a synthetic wax such as Adheso wax manufactured by Glyco Products Co., casein glues rendered waterproof and fungusproof by addition of formaldehyde, rubber cements composed of a solution of natural or synthetic rubber in a solvent such as benzol or the like, solutions of Vinylite resins or of cellulose derivatives such as Celluloid or cellulose acetate, or of natural or synthetic resins in organic solvents, or other suitable waterproof adhesive materials, or mixtures thereof, with or without the addition of plasticizers.

The amount of adhesive should preferably be adjusted so as to impregnate the unparchmentized layers I I to the inner limits of the outer amyloid layers I0, e. g. to a depth of about onehalf to two-thirds of the thickness of each of the sheets, the amyloid preventing any substantial penetration of the adhesive into the printing layers.

When it is desired to modify the printing surface of the plate of my invention for special types of images or copies, for example, when it is desired to impart a grain or tooth to the surface, this may be accomplished by treatment with a coating composition having the desired properties. Thus,

coatings of inorganic mineral materials such as clay, barium sulfate, silica or other finely divided minerals can be applied to a parchment surface of the plate of Fig. 2, either in powdered form or in liquid suspension, or by precipitating them from solution on the face of the plate, such coatings being constituted so as to render the treated surface receptive ltoward greasy image-forming inks when dry, but hydrophilic and grease-repellent when wet. Particular treatments and coatings of the aforesaid nature are known; and may be applied in the manner known to'those skilled in the art. Since such coatings are similar in reaction toward water to the parchmentized surface, they do not detract from the noncurling nature of my plates even when applied to one surface only.

In Fig. 3 of the drawing, I show an enlarged section of a fragment of a plate similar to the plate of Fig. 2, but having on the surface of one amyloid layer I0, a coating I3 of nely divided mineral material as hereinbefore described. Alternatively the modifying material can be applied in solution or suspension capable of penetrating the surface of the amyloid.

Variations and modifications can be made in my invention without departing from the spirit thereof. Thus, a plate similar to that shown in Fig. 2 can be prepared by laminating together two sheets of unparchmentized paper, employing suflicient adhesive to penetrate only from about one-half to two-thirds of the depth of each of the sheets, and after the adhesive is dry, subjecting both sides of the sheet to parchmentizing treatment. Such a procedure however has the disadvantage that the nature and quantity of adhesive must be carefullycontrolled to avoid excessive penetration of the sheets, e. g. to the surface to be parchmentized since there is no layer of amyloid to limit the penetration. Moreover, the amount of adhesive which can be used must generally be limited so that the impregnated layers do not approach saturation to the extent `unifie made possible by the 'usc of preparchmentized sheets, and the composite plate has less resistance to stretching or distortion.

Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. The method of making a planographic plate which comprises parchmentizing two sheets of paper on one side only so as to leave a substantial layer of unparchmentized paper on the other side, bonding the unparchmentized sides of said sheets together with a waterproof adhesive, said adhsesive impregnating the unparchmentized layers of said sheets to a, depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said-sheets, said plate having a substantially unified core of paper fibres impregnated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core.

2. The method of making a planographic plate which comprises parchmentizing two sheets of paper on one side only so as to leave a substantial layer of unparchmentized paper on the other side, bonding the unparchmentized sides of said sheets together with their surfaces in intimate surface contact by means of a waterproof adhesive, said adhesive impregnating the unparchmentized layers of said sheets to a depth limited' substantially by the inner limits of the layers of amyloid forming the opposite surfaces of saidsheets, said plate having a substantially unified core of paper fibres impregnated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core.

3. The method of making a planographic plate which comprises parchmentizing two sheets oi' paper on one side only so as to leave a substantial layer of unparchmentized paper on the othe; side, bonding the unparchmentized sides of said sheets together with a waterproof adhesive, said adhesive substantially saturating the unparchmentized layers of said sheets and being prevented from penetrating beyond said unparchmentized layers by the layers of amyloid forming the opposite surfaces of said sheets, said plate having a substantially unified core of-paper flbres impregnated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core.

4. The method of making a planographic printing plate which comprises parchmentizing two sheets of paper on one side only so as to leave a layer of unparchmentized paper on the other side, equal in depth to about'one-half to twothirds of the thickness of said sheets, bonding the unparchmentized sides of said sheets together with their surfaces in intimate surface contact by means of a waterproof' adhesive, said adhesive impregnating the unparchmentized layers of said sheets to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having -a substantially unied core comprising paper fibre impregnated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core.

5. The method of making a planographic plate which comprises parchmentizing two sheets of paper on one side only so as to leave a substantial layer of unparchmentized paper on the other side, bonding the unparchmentized sides of said sheets together with a waterproof adhesive, said adhesive impregnating the unparchmentized layers of said sheets to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having a substantially unified core of paper fibres impregnated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core, and'coating at least one of the sides of the resulting plate with a composition containing a mineral filler, said composition when dry being receptive toward greasy inks and when wet being hydrophilic and grease-repellent.

6. A laminated sheet for planographie printing comprising two layers of paper, each parchmentized on one side only so as to leave a substantial layer of unparchmentized paper on the opposite side, the unparchmentized sides of said paper being bonded together by means of a waterproof adhesive and impregnated by said adhesive to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having a substantially unified core of paper fibres impregnated with waterproof adhesive and hydrophilic strata of amyloid on the outside of said core.

7. A laminated sheet for planographic printing comprising two layers of paper, each parchmentized on one side only so as to leave a substantial layer of unparchmentized paper on the opposite side, the unparchmentized sides of said paper being bonded together with their surfaces in intimate surface contact by means of a waterproof adhesive and impregnated by said adhesive to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having a substantially unified core of paper fibres impregnated with waterproof adhesive and hydrophilic strata of amyloid on the outside of said core.

8. A laminated sheet for planographic printing comprising two layers of paper, each parchmentzed on one side only so as to leave a substantial layer of unparchmentized paper on the opposite side, the unparchmentized sides of said paper being bonded together by means of a waterproof adhesive, the unparchmentized layers of said sheets being substantially saturated by said adhesive to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite sides of said sheets, said plate having a substantially unified core of paper bres impregnated with waterproof adhesive and hydrophilic strata of amyloid on the outside of said core.

9. A laminated sheet for planographic printing comprising two layers of paper each parchmentized on one side only to a depth corresponding to about one-third to one-half of the thickness of the sheet, the remainder of the sheet being unparchmentized, the unparchmentized sides of said paper being bonded together by means of a Waterproof adhesive and the unparchmentized portions thereof being substantially saturated by said adhesive to a depth limited substantially by the inner limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having a substantially unified core of paper fibres saturated with waterproof adhesive and hydrophilic outer strata of amyloid on the outside of said core.

10. A laminated sheet for planographic printing comprising two layers of paper, each parchmentized on one side only so as to leave a substantial layer of unparchmentized paper on the opposite side, the unparchmentized sides of said 7 4 paper being bonded together bidmeansaf :ivlr- REFERENCES CITED prooi' adhesive and impregna y s ve to a. depth limited substantially by the inner my?, ftiggwggeferens e f mrd m u limits of the layers of amyloid forming the opposite surfaces of said sheets, said plate having 5 UNITED STATES PATENTS a substantially unified core of paper fibres iin- Number Name Date pregnated with waterproof adhesive and hy- 2.134,165 Wescott Oct. 25l 1933 drophilic strata of amyloid on the outside of said 2,154,219 Shepherd Apr. 11, 1939 core, and a coating on at least one amyloid surface 2,205,998 Wescott June 25, 1940 of said sheet of a composition containing a 10. mineral ller, said composition when dry being receptive toward rgreasy ink, and when wet being hydrophilic and grease-repellent.

DOUGLAS A. NEWMAN. 

